Considerable interest has been shown in recent years in the use of prostaglandin (PG) precursors in medicine.
For various reasons it is not practical to administer naturally-occurring prostaglandins such as PGE 1 and PGE 2 to patients. Consequently, considerable attention has focussed on the use of prostaglandin precursors including linoleic acid, .gamma.-linolenic acid (GLA) and dihomo-.gamma.-linolenic acid (DGLA).
Conversion of these materials in the body is believed to be as shown in the FIGURE.
The broad outline of this pathway is well known, and it brings out clearly that a major function of essential fatty acids (EFAs) is to act as precursors for prostaglandins, 1 series PGs being formed from dihomo-.gamma.-linolenic acid (DGLA) and 2 series PGs from arachidonic acid (AA). DLGA and AA are present in food in only small quantities, and the major EFA in food is linoleic acid which is first converted to .gamma.-linolenic acid (GLA) and then to DGLA and AA. The conversion of linoleic acid to GLA is blocked by a high fat and high carbohydrate diet, by ageing and for example by diabetes. Stores of AA in the body in the form of lipid esters are very large indeed. In contrast only small amounts of DGLA ester are present.